University of Illinois Urbana-Champaign

A critical examination of the elliptic face-on view with high eccentricity of the central molecular zone of the galactic center

Oka, Takeshi

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https://hdl.handle.net/2142/107415

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Title
A critical examination of the elliptic face-on view with high eccentricity of the central molecular zone of the galactic center
Author(s)
Oka, Takeshi
Issue Date
2020-06-22
Keyword(s)
Astronomy
Date of Ingest
2020-06-26T03:04:20Z
Abstract
In 1972, Kaifu et al. and Scoville\footnote{Kaifu, N., Kato, T., \& Iguchi, T. 1972, Nature, 238, 105: Scoville, N. Z. 1972, ApJ, 175, L127} claimed the existence at the Galactic center (GC) of a circular Expanding Molecular Ring (EMR) of radius $\sim$ 200 pc from longitude-velocity diagram (($l$,$v$) diagram), of radio absorptions of OH and H$_2$CO, respectively. After the development of a theory of gas motions in a barred potential by Binney et al. (1991) \footnote{Binney, J., Gerhard, O. E., Stark, A. A., Bally, J., \& Uchida, K. I. 1991, MNRAS, 252, 210}, however, this circular shape fell out of favor and instead elliptic orbits of the gas with high eccentricity (the x$_1$ orbit of Lindblad resonance) are now widely believed. Meanwhile a recent ($l$,$v$) diagram obtained from infrared absorption spectra of H$_3^+$ by Oka et al. (2019, 2020)\footnote{Part I: Oka, T., Geballe, T. R., Goto, M., Usuda, T., McCall, B. J., \& Indriolo, N. 2019, ApJ, 883:54(31pp) Part II: Oka et al. 2020 in preparation} in the GC's central 300 pc called the Central Molecular Zone (CMZ) has revived the circular shape of the CMZ. %\hspace{0.05in} Observed gas motions on much larger scales (on the order of 3 kpc Liszt \& Burton 1978\footnote{Liszt, H. S., \& Burton W. B. 1978, ApJ, 226, 790}) and face-on views of external galaxies (e.g. Figure 14 of Kormendy \& Kennycut 2004\footnote{Kormendy, J., Kennicut, Jr., R. C. 2004, ARAA, 42, 60}) provide evidence for the x$_1$ orbit. However, we find the application of the same theory to the CMZ, more than 10 times smaller, where the barred potential is not identified, is unjustified. We believe the face-on view of the CMZ as tracing ellipses with high eccentricity is not real.
Publisher
International Symposium on Molecular Spectroscopy
Type of Resource
Text
Genre of Resource
Conference Paper / Presentation
Language
eng
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http://hdl.handle.net/2142/107415
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Copyright 2020 is held by the Author(s)

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Abstracts & Presentations - 2020 International Symposium on Molecular Spectroscopy PRIMARY